AUTOMATED VO2MAX CALIBRATOR FOR OPEN-CIRCUIT INDIRECT CALORIMETRY SYSTEMS

The complete calibration of indirect calorimetry systems involves simu ltaneous checks of gas analyzers, Volume device, and software, and thi s requires a machine that can mimic accurately and precisely the venti lation and expired gases of an athlete. While previous calibrators hav e been built successfully, none have matched the ventilatory flows pro duced by athletes during high intensity exercise. A calibrator able to simulate high aerobic power ((V) over dot O-2max calibrator) was fabr icated and tested against conventional indirect calorimetry systems th at use chain-compensated gasometers to measure expired volume ((V) ove r dot (E) systems) and calibrated electronic gas analyzers. The calibr ator was also checked against a system that measures inspired volume ( (V) over dot (I) system) with a turbine ventilometer. The pooled data from both (V) over dot (E) and (V) over dot (I) systems for predicted (V) over dot O-2 ranging from 2.9 to 7.9 L.min(-1) and ventilation ran ging from 89 to 246 L.min(-1) show that the absolute accuracy (bias) o f values measured by conventional indirect calorimetry systems compare d with those predicted by the calibrator was excellent. The bias was < 35 mL.min(-1) for (V) over dot O-2 and carbon dioxide production, < 0 .50 L.min(-1) for ventilation ((V) over dot (E BTPS)), -0.02% absolute for the percentage of expired O-2, and +0.02% absolute for the percen tage of expired CO2. Overall, the precision of the measured (V) over d ot O-2, (V) over dot CO2, and (V) over dot (E BTPS) was similar to 1%. This (V) over dot (2max) calibrator is a versatile device that can be used for routine calibration of most indirect calorimetry systems tha t assess the ventilation and aerobic power of athletes.